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Running Head: STATISTICAL METHODS IN EPIDEMIOLOGYStatistical Methods in EpidemiologyName of the StudentName of the UniversityAuthor Note
1STATISTICAL METHODS IN EPIDEMIOLOGYAnswer 1(i)A histogram usually represents the distribution of numerical data of a continuousvariable graphically. Each bar of the histogram usually represents the frequency of thecategory. On the other hand, a kernel density plot is a non-parametric method of plottingthe probability density function of a random variable. Thus, a histogram is a moreappropriate graphical method to describe the frequency distribution of a continuousvariable. (ii)Here, the target is to compare the average weight gain of the two samples, that isthe average one-month weight gain of the infants taking two types of diets A and B. Theequality of means of two groups can be tested using the technique of independent samplet-test. Let μ1 and μ2 be the sample means of population 1 and population 2 respectively, ́X1 and ́X2 be the population means of population 1 and population 2 respectively. Let S12and S22 be the sample variances and n1 and n2 be the sample sizes of population 1 andpopulation 2 respectively. The null hypothesis (H0) and alternate hypothesis (HA) for thistest is usually given as H0: μ1 = μ2 against HA: μ1 ≠ μ2The test statistic for the test is given by t=( ́X1− ́X2)−(μ1−μ2)√S2n1+S2n2
2STATISTICAL METHODS IN EPIDEMIOLOGYWhere, S2 = pooled variance = (n1−1)S12+(n2−1)S22n1+n2−1. In this case both n1 and n2 are equalto 36. The null hypothesis will be accepted if the observed value of t is less than thetabulated value of t and rejected otherwise. The 95% confidence interval for the difference can be given by((μ1−μ2)±t0.05,35√S2n1+S2n2).(iii)To compare the spread or variation for two variables with different measurementscales, the appropriate statistical measure that has to be used is the F-test.
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